Catalytic desulfurization of petroleum hydrocarbons



March 16, 1954 F. W. B. PORTER ET AL CATALYTIC DESULFURIZATION OFPETROLEUM HYDROCARBONS Filed Feb. 28 1951 Jam:

2 Sheets-Sheet l FEEDER/CK WALL/9M BER RQY PURDY AZOETHCOT'T JOH/V E0 W4AN TR/IM 1 0/? 72' R March 16, 1954 F. w. B. PORTER ET AL 2,672,433

CATALYTIC DESULFURIZATION OF PETROLEUM HYDROCARBONS Filed Feb. 28, 19512 Sheets-Sheet 2 FR'DER/C K W/LA/HM 5E7EAM PQPTEE P0-Y PUED Y NOE THCO TT 20% E0 WL A N0 Patented Mar. 16, 1954 UNIT-EDMSTATES 2,672,433 PATENTOFF-ICE Application February 28, 1951, Serial No. 213,176

Claims priority; application Great Britain March 15, 1950 I Claims. (Cl.196-28) 1 p This invention relates to the hydrocatalyticdesulphurisation of petroleum hydrocarbons.

Among the processes which are known for the removal of organicallycombined sulphur from petroleum hydrocarbons is the so calledhydrofining process in which the petroleum hydrocarbons to bedesulphurised are, passed in admixture with hydrogen over asulphur-resistant hydrogenation catalyst at elevated temperature andpressure whereby the organically combined sulphur is converted intohydrogen sulphidewhich may readily be removed from the treatedhydrocarbons the properties of which are not otherwise appreciablyaffected. This process is technically effective for the removal oforganically combined sulphur from petroleum hydrocarbons but is notcommercially attractive in View of the cost of supplying theconsiderable quantity of hydrogen l consumed in the process' It was alsoknown that the hydroforming process produced hydrogen and at the sametime effected a considerable degree of desulphurisation, but by its verynature this process is not applicable in cases where it is desired todesulphurise feedstocks, such as gas oils and aromatic extracts, withoutappreciably affecting the properties of the feedstock other than changesconsequent upon the removal of the organically combined sulphur ashydrogen sulphide. Desulphurisation processes are also known in which asubstance capable of supplying hydrogen under the conditions of thedesulphurisation reaction is added to the feedstock to be desulpnurised,but this is only a special case of hydrofining and suffers from thedisadvantage of the cost of supplying the hydrogen donor and from theadditional disadvantage that the through-put of the feedstock is reduced.by the addition of the considerable quantity of hydrogen donornecessary to supply suflicient hydrogen.

It was then discovered that by careful control of the temperature andpressure and by using a sufficiently activedehydrogenation-hydrogenation catalyst, it was possible to derivesuificient hydrogen by dehydrogenation of naphthenes contained in thefeedstock to enable suificient of the organically combined sulphur inthe feedstock to be converted into hydrogen sulphide, under the sametemperature and pressure conditions, to constitute an effectivedesulphurisation process. This process has been autofining and it hasthe considerable advantage as compared with hydrofiningthat all thehydrogen required for desulphurisation is derived, from the feedstockitself. It was surprising to find that conditions existed under whichthe two reactions of dehydrogenation of naphthenes and. hydrogenation oforganic sulphur compounds. could 2v 7 proceed simultaneously .to theextent necessary to provide a satisfactory catalytic desulphurisationprocess. The process was found to be applicable to a wide variety offeedstocks ranging from naphthas to waxdistillates under the followingset of conditions: 1

Pressure p. s. i. ga

Temperature F-.. 750-800 Space velocity ..v./v./hr 1.0-5.0 Recycle rateC. F./B 2000-4000 The preferred catalyst for use in the autofiningprocess is of the so-called cobalt molybdate type which comprisesmixtures of the oxides of cobalt and molybdenum, or chemical compoundsof cobalt, molybdenum and oxygen, or mixtures of one or both of saidoxides with said compounds either alone or incorporated with a support.It has been found that there is a period at the commencement of each-runduring which the gas make is negligible or non-existent and thedesulphurisation is not at its maximum. This low dehydrogenatingactivity of the catalyst is more noticeable at low feedstock velocitiesand with the heavier feedstocks. It was discovered that the non-activityof the catalyst during the early hours on stream could be largelyovercome by subjecting the catalyst tothe action of hydrogen sulphide orhydrogen sulphide-containing gas prior to its use in the autofiningprocess. 1

The regeneration of the used catalyst may be carried out by burning offthe carbon and sulphur deposits with either a nitrogen/air or steam/airmixture. The following conditions may be employed for regeneration.

Inlet temperature F 800-850 Steam or nitrogen flow v./v./hr 700-900 Airflow v./v./hr 50-60 Inlet oxygen percent mol 1 to 1.5

to maintain the predetermined pressure. In this case, there is acontinuous make of hydrogen; indicating that the hydrogen produced inthedehydrogenation reaction is not being fully utilized in thedesulphurisationreaction. Animproved method of operation was therefored6V1r-;-

w i in w ch iiiehy s n-cqn ai e aseous fraction is i'ebycl'efd thereaction zone and the pressure thereiii allowed to rise to anequilibrium pressure at which the hydrogen evolved equals the hydrogenconsumed. This method of opera tion results in a greater degree ofdesuign ssation and increased on-stream hours for a product of givensulphur content.

The autofining process may be carried out in a static bed reactor or bythe use of the moving bed or fluid catalyst techniques. M I

In the autofining of the light straight-runfe'ed stocks, such asnaphthas and kerosines', there is a considerable excess gas make whichcontains upwards of 80 per cent mol. hydrogen. lie; sulphurisation ofthese light feedstocks is of the I distiuates. crude hi1 and deducedcrude, it is necessary to provide large quantities of hydrogen q e nal etmi -;A s. r s e. re ent inv nto h e c ss sa z b al. i q Whinin l t p tole heada he 9. 49 1 na htha. and ere i es is used to supply hydrogen toan independent hyosena o zo ah By an autofin n processis meant a processm whi h Pe oleum, e d o i passed in v ncur, Q m.-;. n. dm x ure w h h env r aeata ystyh h .semh nes a t f the d hyereeenei h 9 ...eanhihnes aoma w t as v ty t e h ims nai n 1 wee e s l- B14131. seaweeds. n which in t poisoned as asata y tbmh e aq sulp r c m n s. under co emns-9i. em ea re an s r w qhre cee relai dcsp. a de r e a tswhthezia. cee i e iaihe.iee q is seede -.t .-.ae;e. e t Jest su aei a ly in, ex 9.? that sed iquce. suf c t h d w. as v r i sei ie lly seawe s h in th smash h dr n.sulph d a d. t m a the pre s e the e ct o zone the ydr e v i nsflnhife Ies s f o he treated racemes and the hydrogen recycled to the reactionzone as thsble source of hydrogen e excess gas the 'autofin'i'ng zonemay fibz-jtestisieient,ts sdppiy all the'hydrogen 'resuites tithe maleasanc zone admin in any case represent a'considerable saving inhydrogen.

he independent-hydrogenation zonemay 'coniiis't'of a-hyd'rofining-zonefor the treatment of Heavier petroleum -feedstocks such as wa x -dis'- rtillate, crude on 'and reducederude, that cannot be satisfactorilyautofined. On the other hand, tliehydrogenation zone may b'efor carryingout a well known hydrogenation process; such as the conversion of'dii's'dbutylene to 'is'ooetane.

According to a preferred method of carrying the-invention into effect,--a-crude -oil is fractionated for the recovery of a -light fraction,which isfautofined and a. residue, the excess gas make trom theautofining stage being used to hydrofinethe residueor a heavy fractionthereof.

The invention will now be described with refereiice l to the accompanyindiagrams, wherein Figures- 1:3 illiistrate diiierent methods at carrymethe invention into efiect.

='Irl the methods illustrated in Figures land 2, a haphtha heiosinefraction is autoiine'd and the excess gas s dsesto-h'ydrofi'ne a waxdistillate frames. The relative proportions by volume r napnt aykerbsipeand tiig its}; distillate out are approximately 2:1.5 and 2:1 for tworepresentative Iranian crudes, although this may vary considerablyaccording to the length of the wax distillate cut. Thus, if the excessgas make is 50 cubic feet per barrel when autofining thenaphthawkerosine blend, then there are available 75-100 cubic feet perbarrel for the desulphurisation of the wax-distillate or other heavyfraction. Two methods of utilising this excess hydrogen-containing gasfor the desulphurisation of wax distillates are illustrated in Figures 1and 2.

Referring first to Figure l, the naphtha-kerosine blend is fed by a pumpl to the preheater 2 after admixture with the recycle gas. The hotvapours pass downwards through the autofining reactor 4 and afterpassing through the cooler or heat exchanger 5 are separated into twophases in the vessel 6. The liquid phase which contains thedesulphurised kerosine-naphtha blend is passed via line I to astabiliser and distillation unit for separation of the fractions asdesired. The gas phase which contains upwards of per cent mol. hydrogenis split into two streams, one being recycled through line 3 and thebooster 3 to maintain the conditions in the reactor 4 while the other,the excess gas, passes through a control valve 9. The wax-distillatefraction is fed by a pump to into admixture with the excess gas from theautofining system and passes to the preheater H via line it. Thepreheated products pass downward over the catalyst bed 12 through apressure control valve 13 and cooler id to the separator IS. The liquidphase is run ofi via line I! for stabilisation for removal of hydrogensulphide and the gases vented via line 18. v

The reactor 4 and its accompanying system are operated at a, pressure of220 pounds per square inch pressure and the excess gas fed into thewax-distillate stream at +200 pounds per square inch. The wax distillatesection therefore operates as a once through hydrofining process i. 6.with no recycle, and pressure is supplied from the first section so thatan economic hydrogen partial pressureis maintained in the secondsection. If necessary, the relative proportion of hydrogen in the excessgas can be increased by scrubbing out the hydrocarbons but this is notessential, neither is it essential to remove hydro gen sulphide from therecycle or excess gas. The following is a'specific example of thismethod of operation:

EXAMPLE 1 Au'tofining section Feedstock .Iranian naphthakerosinefraction 23-48% vol. on

V crude. Catalyst -s Mixed cobalt and molybdenum oxides on alumina.

War-distillate desulphurisatiqn The method illustrated in Figure 2 isessentially the same as that illustrated in Figure l, the onlydifierence being the provision of a compressor l9 between the twosections to enable the wax-distillate desulphurisation to be carried outat a higher pressure and thereby increase the sulphur removal. Theamount of excess gas from the autofining section can be controlled,within limits, by adjustment of the space velocity. The following is aspecific example of this method of operation:

EXAMPLE 2 Autofining section Feedstock Iranian naphthakerosine fraction848% vol. on

crude. Catalyst Mixed cobalt and molybdenum oxides on alumina. Pressure150 p. s. i. ga. Temperature 780 F. Space velocity 1.0 v./v./hr. Gasrecycle rate 2500 S. C. F./B. Gas hydrogen content 85-90% mol. Excessgas 50 S. C. F./B.

Sulphur content of feed 0.25% wt. Sulphur content of product .002% wt.Sulphur removal 99%.

Wax-distillate desulphurz'sation Iranian wax-distil- Feedstock late cut72%- 82% v o l o n crude.

Catalyst Mixed cobalt and molybdenum oxides on alumina.

Duration of run 50 hours.

Pressur 500 p. s. i. ga.

Temperature 750 F.

Space velocity 1.0 v./v./hr.

Inlet gas rate 200 S. C. F./B.

Sulphur content of feed-.." 1.5% wt. Sulphur content of product- 0.3%wt. Sulphur removal 80%.

It will be noted that to increase the excess gas make in the autofiningsection, the space velocity and pressure have been decreased.

Referring now to Figure 3, crude petroleum stabilised to C. is fed viapreheater 20 to the fractionating tower -2 I where a naphtha-kerosinecut boiling between 20 and 250 C. is taken overhead through condenser 22to the reflux drum 23.

Some of'the naphtha-kerosine is returned to the tower as reflux by thereflux pump 24, the remainder being fed by the feed pump 25 to thepreheater 26. The naphtha-kerosine, together with the recycle gas, isbrought up to reaction temperature and passes into the reactor 21. Theautofined product from the reactor passes out through a waste heatboiler 28 to a knock-out tower 29. The pressure on the waste heat boileris controlled to give an inlettemperature into the knock-out tower suchthat the kerosine is condensed whilst the naphtha and recycle gas passoff the top of the knock-out tower through a cooler 30 to a separator3|. There the recycle gas separates from the liquid naphtha and isrecycled by means of the gas booster 32 to the preheater inlet. Furthercontrol of the knock-out. tower is effected by returning some of thecold. naphtha from the separator as reflux by the.- pump 33. Thekerosine passes from the base of the knock-out tower through a cooler 34to stor-- age. The naphtha passes from the separator to a conventionalstabiliser (not shown) where thedissolved hydrogen sulphide is removed.The.- excess gas, over and above that required to main-- tain the systemunder pressure, is released through the pressure control valve 35 to thecompressor 36. Here, it is compressed to the required operating pressureand passes via the flow controller 3'! into the preheater inlet line,where it meets the residue from the fractionator 2| and passes into thepreheater 38. The gas-residue mixture is brought up to the reactiontemperature in the preheater 38 and passes into the reactor 39.

- The desulphurised product and the gas pass out via a pressure controlvalve 40, which can be used to control the preheater and reactorpressure or which can, if required, be bypassed. Thehydrocarbon-hydrogen stream passes through a cooler 4| to a separator42, where the gas separates from the liquefied product. The gas caneither be vented via the pressure controller 43 or be recycled by therecycle booster 44 to the preheater inlet.

The desulphurised residue is' passed from the separator 42 via astabiliser not shown) to remove dissolved hydrogen sulphide to storage.If required, fresh hydrogen from an external source ma beinjected intothe suction of, the compressor 36 through line 45. The use of controlvalves 40, 43 and 31 and the gas recycle booster 44 depends on whetherit is desired to operate with or without a gas recycle system and/orhydrogen added from an external source. This may be summarised asfollows:

Case 1.Recycle system without external hy drogen.--Booster 44 andpressure controller 43 in use. Valves 40 and 31 lay-passed.

Case 2.-Recycle system with external hydrogen.Booster 44, pressurecontroller 43 and flow controller 31 in use. Valve 40 by-passed.

Case 3.Once-through system without external hydrogen-Valve 40 in use,valves 43 and 31 by-passed and booster 44 shut down.

The following results were obtained for stabilised 20 C. Iranian crude:

Yield distillate (naphtha-kero.) BJB. stable crude=.43. Yield residue250 C.) BJB. stable crude-=57.

Conditions for naphtha-kerdautofining Pressure, p. s. 1. ga -e 100Reactor temp., F 800 Space velocity, v./v./hr 1.0 Recycle rate, S. C.FJB e000 Total sulphur in feed, percent wt; .089

Total sulphur in naphtha product- 001 Total sulphur in kerosine' .001Sulphur removal, percent 98.8

Excess gas (approx. 80 mol. percent Hz) 150 S. C. F./B. naphtha-kerosine =64.5 S. C. F./B. stable crude. :113 S. C. F./B. residue.

Conditions for residue desulphurz'sation Case 3 Pressure, p. s. i. 000500. Reactor Temp, r 750 750. Space Velocity, v./v./h 1.0 1.0. RecycleRate, S. O. F. l, 000 once through. External H2, S. G. FJB. nil 8 nilTotal Sulphur in Feed, percent V6.1 1.81 1. 81 1.8 1. Total Sulphur inProduct.. 1.09 0. 36 0.9. Sulphur Removal, percent 40 80 50.

Inspection data. on residue before and after desulphurz'sation(conditions'asfor Case 2) RESIDUE (BEFORE) The product distribution inCasesl and 3 will be similar to Case 2, except that less lower boilingmaterial will be formed.

Among the advantages of-the process according to the invention are theproduction of a naphtha-kerosine'fraction of low sulphur content, and ofa reduced crude of low sulphur content, of lowered viscosity and with anincreased content of lower boiling material.

We-claim:

1. A process for the recovery of sulphur free products fromnaphthene-containing crude petroleum by thehydrocatalytic.desulphurisation process without the need for anextraneous source of hydrogen, which comprises fractionating the crudepetroleum for therecovery of a selected naphthene-containing low-boilingfraction and a. residue, passing said low-boiling fraction in admixturewith hydrogen derived solely from said fraction to a firstdesulphurisation zone wherein it is contacted with a sulphur-resistantdehydrogenation-hydrogenation catalyst which is immuneto sulphurpoisoning and combines activity for the dehydrogenation of naphthenes toaromatics with activity for the hydrogenation of organically combinedsulphur in said fraction to hydrogen sulphide at a selected temperaturewithin the range 750-800 F. and a selected pressure within the range-250 p. s. 1. ga., said temperature and pressure being correlated sothat organically combined sulphur in said fraction is converted intohydrogen sulphide and hydrogen is produced by dehydrogenation ofnaphthenes contained in said low-boiling fraction in an amount in excessor that required to convert organically combined sulphur contained insaid low-boiling fraction into hydrogen sulphide and maintain thenecessary partial pressure of hydrogen in said zone, separating hydrogensulphide and a lwdrogen-rich gas mixture from the products of said firstdesulphurisation zone, recycling a portion of said hydrogen-rich gasmixture to said first desulphurisation zone to constitute the Whole ofthe hydrogen supplied to said zone, the hydrogen recycle rate beingsufiicient to maintain the necessary partial pressure of hydrogen insaid zone therein, passing another portion of said hydrogen-rich gasmixture in admixture with said residue to a second desulphurisation zonewherein said residue is contacted with a sulphur-resistant hydrogenationcatalyst and hydrogen of the mixture at a temperature and pressuresuitable for hydrofining of said residue whereby organically combinedsulphur contained in said residue is converted into hydrogen sulphide,said hydrogen-rich gas mixture constituting the sole source of hydrogensupplied to said hydrofining stage, separating hydrogen sulphide fromthe products of said second desulphurisation zone, and recovering asubstantially sulphur-free product from both said desulphurisationzones.

2. A process in accordance with claim 1 in which a hydrogen-rich gasmixture is obtained from the second desulphurisation zone and isrecycled to the second desulphurisation zone.

3. A process in accordance with claim 1 wherein the recoveredlow-boiling fraction comprises the naphtha and kerosene fractions.

4. A process in accordance with claim 1 wherein the sulphur-resistantdehydrogenation-hydrogenation catalyst is a cobalt molybdate type.

5. A process inaccordance with claim 1 wherein the low-boiling fractioncomprises the naphtha and kerosene fractions and thedehydrogenationhydrogenation catalyst is a cobalt molybdate type.FREDERICK WILLIAM BER'I'RAM PORTER. ROY PURDY NORTHCOTT.

.JOI-IZN ROWLAND.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,417,308 Lee Mar. 11, 1947 2,486,361 Nahin et al Oct. 25,1949 2,567,252 Strang Sept. 11, 1951 2,573,726 Porter et a1 NOV. 6, 1951

1. A PROCESS FOR THE RECOVERY OF SULPHUR-FREE PRODUCTS FROMNAPHTHENE-CONTAINING CRUDE PETROLEUM BY THE HYDROCATALYTICDESULPHURISATION PROCESS WITHOUT THE NEED FOR AN EXTRANEOUS SOURCE OFHYDROGEN, WHICH COMPRISES FRACTIONATING THE CRUDE PETROLEUM FOR THERECOVERY OF A SELECTED NAPHTHENE-CONTAINING LOW-BOILING FRACTION AND ARESIDUE, PASSING SAID LOW-BOILING FRACTION IN ADMIXTURE WITH HYDROGENDERIVED SOLELY FROM SAID FRACTION TO A FIRST DESULPHURISATION ZONEWHEREIN IT IS CONTACTED WITH A SULPHUR-RESISTANTDEHYDROGENATION-HYDROGENATION CATALYST WHICH IS IMMUNE TO SULPHURPOISONING AND COMBINES ACTIVITY FOR THE DEHYDROGENATION OF NAPHTHENES TOAROMATICS WITH ACTIVITY FOR THE HYDROGENATION OF ORGANICALLY COMBINEDSULPHUR IN SAID FRACTION TO HYDROGEN SULPHIDE AT A SELECTED TEMPERATUREWITHIN THE RANGE 750-800* F. AND A SELECTED PRESSURE WITHIN THE RANGE50-250 P. S. I. GA., SAID TEMPERATURE AND PRESSURE BEING CORRELATED SOTHAT ORGANICALLY COMBINED SULPHUR IN SAID FRACTION IS CONVERTED INTOHYDROGEN SULPHIDE AND HYDROGEN IS PRODUCED BY DEHYDROGENATION OFNAPHTHENES CONTAINED IN SAID LOW-BOILING FRACTION IN AN AMOUNT IN EXCESSOF THAT REQUIRED TO CONVERT ORGANICALLY COMBINED SULPHUR CONTAINED INSAID LOW-BOILING FRACTION INTO HYDROGEN SULPHIDE AND MAINTAIN THENECESSARY PARTIAL PRESSURE OF HYDROGEN IN SAID ZONE, SEPARATING HYDROGENSULPHIDE AND A HYDROGEN-RICH GAS MIXTURE FROM THE PRODUCTS OF SAID FIRSTDESULPHURISATION ZONE, RECYCLING A PORTION OF SAID HYDROGEN-RICH GASMIXTURE TO SAID FIRST DESULPHURISATION ZONE TO CONSTITUTE THE WHOLE OFTHE HYDROGEN SUPPLIED TO SAID ZONE, THE HYDROGEN RECYCLE RATE BEINGSUFFICIENT TO MAINTAIN THE NECESSARY PARTIAL PRESSURE OF HYDROGEN INSAID ZONE THEREIN, PASSING ANOTHER PORTION OF SAID HYDROGEN-RICH GASMIXTURE IN ADMIXTURE WITH SAID RESIDUE TO A SECOND DESULPHURISATION ZONEWHEREIN SAID RESIDUE IS CONTACTED WITH A SULPHUR-RESISTANT HYDROGENATIONCATALYST AND HYDROGEN OF THE MIXTURE AT A TEMPERATURE AND PRESSURESUITABLE FOR HYDROFINING OF SAID RESIDUE WHEREBY ORGANICALLY COMBINEDSULPHUR CONTAINED IN SAID RESIDUE IS CONVERTED INTO HYDROGEN SULPHIDE,SAID HYDROGEN-RICH GAS MIXTURE CONSTITUTING THE SOLE SOURCE OF HYDROGENSUPPLIED TO SAHD HYDROFINING STAGE, SEPARATING HYDROGEN SULPHIDE FROMTHE PRODUCTS OF SAID SECOND DESULPHURISATION ZONE, AND RECOVERING ASUBSTANTIALLY SULPHUR-FREE PRODUCTS FROM BOTH SAID DESULPHURISATIONZONES.